I have this error in JS Console, when I try to add a course :
fitness-planning-manage-workouts.js?ver=1.3.8:147 Uncaught TypeError: Cannot read property ‘start’ of null
at fitness-planning-manage-workouts.js?ver=1.3.8:147
at Function.each (load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-ui-mouse,jquery-ui-draggable,utils&ver=5.3.4:2)
at HTMLButtonElement.<anonymous> (fitness-planning-manage-workouts.js?ver=1.3.8:143)
at HTMLButtonElement.dispatch (load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-ui-mouse,jquery-ui-draggable,utils&ver=5.3.4:3)
at HTMLButtonElement.r.handle (load-scripts.php?c=0&load[chunk_0]=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-ui-mouse,jquery-ui-draggable,utils&ver=5.3.4:3)